This invention generally pertains to a system including a plurality of machine units each provided with an internal computer and, more particularly, relates to a method of mutually transmitting data between individual machine units.
Various types of game machines used in amusement businesses are known examples of a local area network (hereinafter referred to as LAN) system which comprises discrete devices (or unit machines) each incorporating a computer of the same performance level. It is known that some of these game machines are constructed in such a manner that individual machine units can operate fully independently of other machine units, while they can also work interactively, allowing each player to compete with other players.
In various systems comprising a plurality of machine units interacting with each other, like the aforementioned game machines, it is essential that various data generated in one machine be sent to the other machines so that each machine can work in a proper interrelationship with the other machines. For this reason, operation data and processed data are exchanged between one user machine and another in such systems.
FIG. 4 is a general arrangement diagram showing a conventional method in mutual data transmission. As depicted in the diagram, a LAN system 1 comprises five computers, that is, a first computer 11, a second computer 12, a third computer 13, a fourth computer 14 and a fifth computer 15, individually contained in separate machines. These computers 11-15 incorporates first to fifth memories 21-25, respectively. Data produced as a result of user operations at the individual machines are entered and stored in the respective internal memories 21-25. These data are exchanged between different computers each time the data are updated or at appropriate time intervals.
FIG. 5 is a diagram illustrating a typical structure of the aforementioned transmitted data. Each set of data 4 includes a predefined number of bits, e.g., 1 kilobit (=2.sup.10 bits=1024 bits) as illustrated. Such data is exchanged between the individual computers 11-15 of the LAN system 1 via a communications network 3 which connects the computers 11-15 in series.
The communications network 3 includes, for example, a first transmission way 31 between the first and second computers 11-12, a second transmission way 32 between the second and third computers 12-13, a third transmission way 33 between the third and fourth computers 13-14, and a fourth transmission way 34 between the fourth and fifth computers 14-15, as illustrated in FIG. 4. Data 4 stored in the first memory 21 is transmitted to the second memory 22 via the first transmission way 31 at the beginning. Then, data 4 stored in the second memory 22, including the data 4 received from the first memory 21, is transmitted to the third memory 23 via the second transmission way 32. This data transmission process is sequentially executed until data 4 stored in the fourth memory 24 is transmitted to the fifth memory 25 via the fourth transmission way 34. Thereafter, data 4 is transmitted from the fifth memory 25 to the fourth memory 24 via the fourth transmission way 34, from the fourth memory 24 to the third memory 23 via the third transmission way 33, and so on up to the first memory 21 in succession.
FIGS. 6A-6D and 7A-7D depict the concept of the aforementioned data transmission sequence. In these diagrams, data 4 stored in the first to fifth memories 21-25 at the beginning are expressed as different sets of data items, that is, first data 4a, second data 4b, third data 4c, fourth data 4d and fifth data 4e, respectively. Among the four transmission ways 31-34, an active transmission way (through which data is currently flowing) is represented by a thick line with arrow. Furthermore, data 4 just transmitted through an active transmission way shown by a thick line with arrow is shaded with a halftone dot pattern.
More particularly, the first data 4a in the first memory 21 is transmitted via the first transmission way 31 and stored into the second memory 22 as shown by dot shading in FIG. 6A at first. Next, the first data 4a and second data 4b stored in the second memory 22 are transmitted together via the second transmission way 32 and stored into the third memory 23 as shown in FIG. 6B. The first data 4a, second data 4b and third data 4c stored in the third memory 23 are transmitted together via the third transmission way 33 and stored into the fourth memory 24 as shown in FIG. 6C. The first to fourth data 4a-4d stored in the fourth memory 24 are then transmitted together via the fourth transmission way 34 and stored into the fifth memory 25 as shown in FIG. 6D.
After the above-described sequence of forward-going data transmission, data 4 is transmitted in the backward direction starting from the fifth memory 25 down to the first memory 21 to fill up insufficiencies of their data contents.
Specifically, the fifth data 4e is transmitted to the th memory 24 via the fourth transmission way 34 as shown in FIG. 7A at first. The fourth data 4d and fifth data 4e are transmitted to the third memory 23 via the third transmission way 33 as shown in FIG. 7B. The third data 4c, fourth data 4d and fifth data 4e are transmitted to the memory 22 via the second transmission way 32 as shown in FIG. 7C. Then, the second to fifth data 4b-4e are transmitted to the first memory 21 via the first transmission way 31 as shown in FIG. 7D so that all the memories 21-25 eventually have the same data 4a-4e.
According to the above-described conventional method in mutual data transmission, if the LAN system 1 comprises five computers, eight steps are required to complete a data transmission sequence. Generally, if the LAN system 1 comprises n computers, (n-1).times.2 steps of data transmission are required. This means that the conventional method entails an extremely complicated data transmission sequence.
Furthermore, assuming that the length of data 4 is 1 kilobit and each step of data transmission takes one second, for instance, 20 kilobits of data must be exchanged to complete data transmission to all the machines, requiring 20 seconds in total, in the example shown in FIGS. 6A-6D and 7A-7D.
Another known approach is to form a ring network by providing an additional transmission way to connect between the first computer 11 and fifth computer 15 as shown by an alternate long and short dash line in FIG. 4. In this approach, it will be possible to reduce the overall data transmission time if all the computers 11-15 in the ring network are arranged to transmit and receive data 4 in synchronism with each other. However, there exist considerable technical difficulties in synchronizing their transmit and receive operations. Another problem of this arrangement is that if a failure occurs in one of the computers 11-15, it becomes impossible to transmit data 4 to the other computers.